Quite akka when remote lifecycle logging is disabled.

I noticed when connecting to a standalone cluster Spark gives a bunch
of Akka ERROR logs that make it seem like something is failing.

This patch does two things:

1. Akka dead letter logging is turned on/off according to the existing
   lifecycle spark property.
2. We explicitly silence akka's EndpointWriter log in log4j. This is necessary
   because for some reason that log doesn't pick up on the lifecycle
   logging settings. After a few hours of debugging this was the only solution
   I found that worked.
Provide logging when attempts to connect to the master fail.

Without these it's a bit less clear what's going on for the user.

One thing I realize when doing this is that akka itself actually retries
the initial association. So the retry we currently have is redundant with
akka's.
Responding to Aaron's review
Allow users to set arbitrary akka configurations via spark conf.
Allow configuration to be printed in logs for diagnosis.